Groundwater isotopic signals in the Perth Basin: links to recharge variations and climatic conditions for Western Australia

Meredith, KT; Cendón, DI; Hollins, SE; Pigois, JP; Schafer, D; Koomberi, H

Groundwater isotopic signals in the Perth Basin: links to recharge variations and climatic conditions for Western Australia

Date

2013-09-20

Authors

Publisher

International Association of Hydrogeologists

Abstract

Perth Basin aquifers contain large volumes of groundwater that support ecosystems and an ever increasing demand for irrigation and potable water supply for Western Australia. Applying isotopic tools to groundwaters contained in regional aquifer systems can provide information on recharge intensity, source and past climatic conditions for the region. Large regional aquifer systems, contained within the Perth Basin, were investigated in this study to provide information on climate interaction over the past ~30 ka. The development of regional scale databases containing groundwater age and isotopic records are not common in Australia and are generally more site specific. Therefore, this database from the Perth Basin provides us with a unique opportunity to study and interpret a low-resolution palaeo-archive of groundwater recharge signals for the West of Australia. Groundwater ages (14CDIC) and Stable Water isotope (SWI: δ18/16O and δ2H) data are presented for the Perth Basin. We compare this data with the cyclone impacted recharge areas of the Pilbara region in the far north of Western Australia. We have gathered all known age and SWI data from the Perth Basin and have focused more specifically on the central (near Gingin) and northern (near Geraldton) Perth Basin. Groundwater ages for the Perth Basin span the radiocarbon dating period from 0 to ~35 ka. SWI results plot to the left of the Global and Perth Meteoric Water Lines but when compared with groundwaters from the Pilbara region, are much more enriched indicating different recharge events replenishing the Perth Basin aquifers compared to the north of Western Australia. Cyclic patterns in SWI over the past 35 ka are observed but generally all data plot around -20.0 ± 5.0 % for δ2H (n = >200). Interestingly, the similarity in values over the past 35 ka is not what is observed in other regional aquifers throughout the world such as in Europe and Africa. Groundwater isotopic signatures are compared with higher resolution archives such as rainfall records to interpret the observed groundwater signal. The isotopic signals contained in these extensive groundwater systems may provide information on past climates and more importantly provide understanding on how climate change is likely to influence recharge of these vast groundwater resources.

Keywords

Isotopes, Western Australia, Groundwater recharge, Climates, Aquifers, Data, Carbon 14, Ecosystems

Citation

Meredith, K., Cendon, D., Hollins, S., Pigois, J. P., Schafer, D., & Koomberi, H. (2013). Groundwater isotopic signals in the Perth Basin: links to recharge variations and climatic conditions for Western Australia. Paper presented to IAH 2013 Perth Australia : "Solving the groundwater challenges of the 21st century", International Association of Hydrogeologists 40th International Conference, Perth, Western Australia, 15-20 September 2013, (pp. 206).